Biosphere 2

Biosphere 2, located at 32540 South Biosphere Road in Oracle, Arizona, is the world's largest Earth systems science research facility — a series of glass and steel enclosed biome structures covering 3.14 acres built between 1987 and 1991 by Space Biosphere Ventures. The name distinguishes it from Biosphere 1, which refers to Earth itself. The facility's original mission was to test whether a completely closed ecological system could sustain human life independently — a concept central to planning for long-duration space habitation. In two dramatic early experiments, eight 'bionauts' lived sealed inside for a two-year mission from 1991 to 1993, growing their own food and recycling all air, water, and waste within the sealed structure. A second, shorter crew mission followed in 1994. The experiments yielded important data on closed ecosystem dynamics, the interactions of soil, atmosphere, water, and living organisms, and the psychological dimensions of long-term group isolation. Since 1996 the facility has been operated by the University of Arizona as a research and education center, with ongoing scientific experiments in climate change, ecology, and water cycling. Guided tours traverse all five original biome sections: the Tropical Rainforest dome, the Tropical Ocean with its 700,000-gallon salt water tank and coral reef, the Mangrove Wetlands, the Savannah Grassland, and the Fog Desert biome. Tours also include the 'lung' — two massive steel chamber domes that expand and contract with temperature changes to equalize pressure inside the sealed structure, a critical piece of engineering that makes the sealed environment viable. The site is located in the Santa Catalina foothills at 3,900 feet elevation, 38 miles north of Tucson.